The present invention relates to a light-sensitive silver halide photographic material and, more particularly, to a photographic material which generates less fluctuation in photographic capabilities after storage and generates less fluctuation in photographic capabilities after photographing until development processing.
Further, the present invention relates to a silver halide photographic material which generates less fog.
Still further, the present invention relates to a novel hydroxamic acid based compound which provides photographically useful effect.
In a silver halide color photographic material, it is required, as well as high sensitivity, that fluctuations in photographic characteristics are less during storage after manufacture of a photographic material and also after photographing until development processing.
Of the fluctuations in photographic characteristics after photographing until development processing, with respect to the prevention of latensification, a method by the combined use of a hardening agent having an active vinyl group with a triazine based compound is disclosed, for example, in JP-A-59-162546 (the term xe2x80x9cJP-Axe2x80x9d as used herein means an xe2x80x9cunexamined published Japanese patent applicationxe2x80x9d).
However, the above method is not sufficient in the preventing effect and a further improvement has been desired.
On the other hand, in a full color photographic material, a multilayer structure comprising a plurality of emulsions having different spectral sensitivities is used to achieve the object of a full color photograph. However, although the emulsions for such a usage have been considerably improved, fog, intensification and fading of a latent image are liable to occur, therefore, they are not necessarily sufficient. 2-Hydroxyamino-1,3,5-triazines, for example, are useful for the improvement of such storage stabilities. However, the above storage stability improver used in each layer varies according to the emulsion used in each layer. Accordingly, a method to improve the storage stability of the latent image of the emulsion of rather a specific layer has been strongly desired in recent years.
Many of known 2-hydroxylamine-1,3,5-triazines are diffusible, therefore, these compounds have a drawback such that their function is exerted also to emulsions of layers other than the objective layer. On the other hand, hydroxamic acids having specific structures are disclosed in JP-A-59-198453 and JP-A-3-293666, but their use purposes are different from the object of the present invention and, further, their effect of the improvement of the storage stability of a latent image and the function to the emulsion of solely a specific layer are not sufficient. Accordingly, the development of a method to largely improve the storage stability of the latent image of only the objective layer has been strongly desired.
The present invention is to provide a method for improving the above-described storage stability of the emulsion and the stability of the latent image of a specific layer.
The present inventors have eagerly studied the method of improving the storage stability of an emulsion produced and the storage stability of a latent image to solve the above problems. As a result of various investigations particularly about the carbon atom number and the kind of substituents of storage stability improvers, a completely novel N-alkylhydroxamic acid based compound of the present invention which has a specific substituent and a carbon atom number has been discovered.
Further, it has been found that the compound of the present invention can achieve the objects of the present invention, when added to a silver halide photographic material, without changing the hue of the dye formed, affecting the dye-forming speed of a coupler, accelerating the decomposition of a coupler and the dye formed, deteriorating the film strength, or fogging an emulsion.
Still further, it has been found that the hydroxamic acid based compound according to the present invention shows a sufficient improving effect of the storage stability of a latent image and an emulsion with a reduced amount of addition.
Moreover, the compound according to the present invention is a completely novel compound which has not been known in the past. The photographic usefulness of this compound has become clear solely by the investigations of the present inventors.
One object of the present invention is to provide a compound which is very effective to improve the storage stability of a silver halide emulsion and the storage stability of a latent image and also to provide a method for improving the storage stability of a latent image using said compound.
Another object of the present invention is to provide a compound which can improve the storage stability of the latent image of solely a specific layer and also to provide a method for improving the storage stability of a latent image using said compound.
A further object of the present invention is to provide a compound which can improve the storage stability of a latent image without adversely affecting various photographic characteristics when added to a photographic material and also to provide a method for improving the storage stability of a latent image using said compound.
A still further object of the present invent on is to provide a compound which can achieve a sufficient improvement of the storage stability of a latent image and the storage stability of an emulsion with a reduced amount of addition.
The above objects of the present invention have been achieved by the following (1), (2) and (3).
(1) A silver halide photographic material which contains the compound represented by the following formula (I): 
wherein R1 represents a substituted or unsubstituted alkylene group having from 1 to 5 carbon atoms; X represents a water-soluble group; and R represents a substituted or unsubstituted alkyl group having the sum total of from 14 to 40 carbon atoms, an alkenyl group, an aryl group, an alkoxyl group, xe2x80x94NR3R4 (R3 and R4 each independently represents an alkyl group having from 1 to 40 carbon atoms, a hydrogen atom, or an aryl group), a bicycloalkyl group, a bicycloalkenyl group, a cycloalkyl group, a cycloalkenyl group or a heterocyclic group, provided that when X represents a quaternary ammonium salt structure, R2 does not represent an alkyl group having from 14 to 17 carbon atoms.
(2) The silver halide photographic material described in the above (1), wherein R1 represents a substituted or unsubstituted alkylene group having from 1 to 5 carbon atoms; and X represents a water-soluble group selected from the structures represented by the following formula (II), (III), (IV) or (V): 
wherein Ra, Rb and Rc, which may be the same or different, each independently represents a substituted or unsubstituted alkyl group having from 1 to 5 carbon atoms or a hydrogen atom; and Axe2x88x92 represents a monovalent anion;
xe2x80x94SO3xe2x88x92.B+xe2x80x83xe2x80x83(III)
wherein B+ represents a monovalent cation;
"Parenopenst"Oxe2x80x94L"Parenclosest"nOxe2x80x94Rdxe2x80x83xe2x80x83(IV)
wherein L represents a substituted or unsubstituted alkylene group having from 2 to 4 carbon atoms; n represents an integer of from 2 to 8; and Rd represents a hydrogen atom, a substituted or unsubstituted alkyl group having prom 1 to 4 carbon atoms, or a substituted or unsubstituted aryl group having from 6 to 10 carbon atoms; 
wherein M represents a hydrogen atom or a metal atom; and R2, when X has the structure represented by formula (II), represents a substituted or unsubstituted alkyl group having the sum total of from 18 to 40 carbon atoms, a substituted or unsubstituted alkenyl group having the sum total of from 14 to 40 carbon atoms, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkoxyl group, xe2x80x94NR3R4 which may be substituted (R3 and R4 each independently represents an alkyl group having from 1 to 40 carbon atoms, a hydrogen atom, or an aryl group), a substituted or unsubstituted bicycloalkenyl group, a substituted or unsubstituted bicycloalkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted cycloalkenyl group or a substituted or unsubstituted heterocyclic group, and when X has the structure represented by formula (III), (IV) or (V), R2 represents a substituted or unsubstituted alkyl group having the sum total of from 14 to 40 carbon atoms, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted alkoxyl group, xe2x80x94NR3Rxe2x88x9dwhich may be substituted (R3 and R4 each independently represents an alkyl group having from 1 to 40 carbon atoms, a hydrogen atom, or an aryl group), a substituted or unsubstituted bicycloalkenyl group, a substitutes or unsubstituted bicycloalkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted cycloalkenyl group or a substituted or unsubstituted heterocyclic group.
(3) A compound represented by formula (VI): 
wherein R2 represents a straight chain alkyl group having from 14 to 23 carbon atoms, a substituted aryl group having the sum total of from 20 to 50 carbon atoms, or a substituted alkyl group having the sum total of from 14 to 40 carbon atoms; and R1 represents an unsubstituted alkylene group having from 1 to 3 carbon atoms.
The compound represented by formula (I) will be explained in detail below.
In formula (I), R1 represents a substituted or unsubstituted alkylene group having from 1 to 5 carbon atoms. When R1 represents a substituted alkylene group, substituents thereof include, e.g., an alkyl group, an alkenyl group, an aryl group, a heterocyclic group, a halogen atom, an alkoxyl group, an aryloxy group, an alkylthio group, an arylthio group, a cyano group, a nitro group, an alkoxycarbonyl group, an aryloxycarbonyl group, a hydroxyl group, an acyl group, an acyloxy group, an alkyl- or arylsulfonyl group, an acylamino group, and an alkyl- or arylsulfonamido group.
The substituted alkylene group preferably has the sum total of from 1 to 10 carbon atoms.
Specific examples thereof include the following structures. 
R1 preferably represents an unsubstituted alkylene group, more preferably an unsubstituted alkylene group having from 1 to 3 carbon atoms, and still more preferably a methylene group.
X represents a water-soluble group. Examples of water-soluble groups include a carboxylic acid group (and the salts thereof), a sulfonic acid group (and the salts thereof), a quaternary ammonio group, a group having a polyether structure having at least 3 or more oxygen atoms, a group having a polyamine structure having at least 3 or more nitrogen atoms, a phosphoric acid residue, and a phosphorous acid residue.
Specific examples thereof include the following structures. 
X preferably represents the structure represented by formula (II), (III), (IV) or (V).
In formula (II), Ra, Rb and Rc, which may be the same or different, each independently represents a substituted or unsubstituted alkyl group having from 1 to 5 carbon atoms or a hydrogen atom, and preferably represents a substituted or unsubstituted alkyl group having from 1 to 5 carbon atoms.
The alkyl group used in the specification of the present invention includes a branched, straight chain, or cyclic alkyl group.
Further, the substituted alkyl group includes an alkyl group which has a heterocyclic structure by a substituent. For example, a 2-furyl group and a 2-piperidino group can be cited as examples of substituted alkyl groups.
Examples of substituents for substituted alkyl groups represented by Ra, Rb and Rc include a carboxyl group, a sulfo group, an aryl group, a cyano group, a nitro group, an arylcarbonyl group, an alkylcarbonyl group, a carbamoyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acylamino group, an aryloxycarbonylamino group, an alkoxycarbonylamino group, an arylsulfonylamino group, an alkylsulfonylamino group, an aminocarbonylamino group, a sulfamoylamino group, xe2x80x94NR5R6 (R5 and R6, which may be the same or different, each independently represents an alkyl group, an aryl group or a hydrogen atom), an alkoxyl group, an aryloxy group, a heterocyclic oxy group, an alkylthio group, an arylthio group, a heterocyclic thio group, an alkylsulfonyl group, an arylsulfonyl group, a phosphoryl group, a halogen atom, a hydroxyl group, an acyloxy group, an alkenyl group and a heterocyclic group.
Of these, an alkoxyl group, an aryloxy group, an alkoxycarbonyl group, an aryloxycarbonyl group, a carbamoyl group, xe2x80x94NR5R6 (R5 and R6, which may be the same or different, each independently represents an alkyl group, an aryl group or a hydrogen atom), and an aryl group are preferred as substituents.
Specific examples of substituents will be described in detail in the explanation of R2 below.
Specific examples of Ra, Rb and Rc include methyl, ethyl, isopropyl, n-butyl, n-propyl, n-heptyl, 2-cyanoethyl, 2-chloroethyl, and 3-methoxypropyl.
The case where all of Ra, Rb and Rc represent the same substituents is preferred to the case where Ra, Rb and Rc each represents different substituents.
The case where all of Ra, Rb and Rc represent unsubstituted alkyl groups having from 1 to 5 carbon atoms is more preferred.
Axe2x88x92 represents a monovalent anion. Specific examples thereof include a chlorine anion, a bromine anion, an iodine anion, an acetic acid anion, and a p-toluenesulfonic acid anion. A xc2xd part of a divalent anion and a ⅓ part of a trivalent anion nay also be included. Specific examples thereof include a xc2xd sulfuric acid dianion, a xc2xd oxalic acid dianion, and a ⅓ phosphoric acid trianion.
Of these, A preferably represents a chlorine anion or a bromine anion.
Preferred structure of formula (II) is such that Ra, Rb and Rc all represent unsubstituted alkyl groups having from 1 to 5 carbon atoms and A represents a chlorine ion. More preferably, Ra, Rb and Rc all represent methyl groups and Axe2x88x92 represents a chlorine ion.
In formula (III), B+ represents a monovalent cation.
Specific examples thereof include a sodium cation, a potassium cation, and a lithium cation. A xc2xd part of a divalent cation may also be included. Specific examples thereof include a xc2xd calcium dication and a xc2xd magnesium dication. Further, quaternary ammonium may also be included.
Of these, B+ preferably represents a sodium cation or a potassium cation.
In formula (IV), L represents a substituted or unsubstituted alkylene group having from 2 to 4 carbon atoms. Substituents described in Ra, Rb and Rc can be cited as substituents thereof.
L preferably represents an unsubstituted alkylene group having from 2 to 4 carbon atoms, and most preferably an ethylene group.
n represents an integer of from 2 to 8, preferably from 2 to 5, and most preferably 3.
Rd represents a hydrogen atom, a substituted or unsubstituted alkyl group having from 1 to 4 carbon atoms, or a substituted or unsubstituted aryl group having from 6 to 10 carbon atoms.
When Rd represents a substituted alkyl group, those described as substituents when Ra, Rb and Rc each represents a substituted alkyl group can be cited as substituents of the substituted alkyl group. When Rd represents an alkyl group, an unsubstituted alkyl group is preferred to a substituted alkyl group.
When Rd represents an alkyl group, specific examples thereof include methyl, ethyl, n-propyl, isopropyl, t-butyl, n-butyl, 2-cyanoethyl and 2-chloroethyl.
When Rd represents an alkyl group, a methyl group is most preferred.
When Rd represents a substituted aryl group, those described as substituents when Ra, Rb and Rc each represent a substituted aryl group can be cited as substituents of the substituted aryl group.
When Rd represents an aryl group, an unsubstituted aryl group is preferred to a substituted aryl group.
Specific examples of aryl groups include phenyl, p-methoxyphenyl, and o-chlorophenyl.
When Rd represents an aryl group, a phenyl group is most preferred.
It is preferred for Rd to represent an alkyl group to an aryl group.
Rd most preferably represents a methyl group.
Preferred structure of formula (IV) is such that L represents an unsubstituted alkylene group having from 2 to 4 carbon atoms, n represents from 2 to 5 and Rd represents an unsubstituted alkyl group having from 1 to 4 carbon atoms.
The most preferred structure of formula (IV) is such that L represents an ethylene group, n represents 3 and Rd represents a methyl group.
In formula (V), M represents a hydrogen atom or a metal atom. When M represents a metal atom, formula (V) becomes xe2x80x94COxe2x80x94Oxe2x88x92 M+. M+ represents a monovalent metal cation, and examples thereof include those cited as specific examples of B+in formula (III). Above all, a potassium ion and a sodium ion are preferred.
Of the structures represented by formula (II), (III), (IV) or (V), X is preferably represented by formula (V) and, above all, the case where M represents a hydrogen atom is preferred.
R2 in formula (I) is described below.
When X is the structure represented by formula (II), R2 represents a substituted or unsubstituted alkyl group having the sum total of from 18 to 40 carbon atoms, an alkenyl group having the sum total of from 14 to 40 carbon atoms, an aryl group, an alkoxyl group, xe2x80x94NR3R4 (R3 and R4 each independently represents an alkyl group having from 1 to 40 carbon atoms, a hydrogen atom, or an aryl group), a bicycloalkenyl group, a bicycloalkyl group, a cycloalkyl group, a cycloalkenyl group or a heterocyclic group.
When X is the structure represented by formula (III), (IV) or (V), R2 represents a substituted or unsubstituted alkyl group having the sum total of from 14 to 40 carbon atoms, an alkenyl group, an aryl group, an alkoxyl group, xe2x80x94NR3R4 (R3 and R4 each independently represents an alkyl group having from 1 to 40 carbon atoms, a hydrogen atom, or an aryl group), a bicycloalkenyl group, a bicycloalkyl group, a cycloalkyl group, a cycloalkenyl group or a heterocyclic group.
The alkyl group is a substituted or unsubstituted straight chain or branched alkyl group.
When the alkyl group is an unsubstituted straight chain alkyl group, the alkyl group preferably has from 15 to 30 carbon atoms. Specific examples thereof include palmityl, eicosyl and docosyl.
When the alkyl group is an unsubstituted branched alkyl group, the alkyl group preferably has from 17 to 30 carbon atoms. Specific examples thereof include the following structures: 
When X is represented by formula (II) and R2 represents an unsubstituted alkyl group, R2 preferably has from 18 to 30 carbon atoms. Further, when X is represented by formula (III), (IV) or (V) and R represents an unsubstituted alkyl group, R2 preferably has from 15 to 30 carbon atoms.
When R2 represents a substituted alkyl group, those described as substituents when Ra, Rb and Rc each represents a substituted alkyl group can be cited as substituents of the substituted alkyl group.
R2 in formula (I) will be further described in detail. When R2 represents a substituted alkyl group, preferred examples of substituents thereof include an alkoxyl group (an alkoxyl group having from 1 to 39 carbon atoms, e.g., methoxy, ethoxy, n-propoxy, isopronaoxy, n-pentoxy, n-hexyloxy, n-otyloxy, n-butoxy, stearyloxy, dodecyloxy, eicosyloxy, docosyloxy), in addition to the above, alkoxyl groups derived from higher alcohols such as Fine Oxocol 140, 1600, 1800, 180, 180N, 2000 and 2600 (trade names, produced by Nissan Chemical Industries, Ltd.) can also be included in specific examples of alkoxyl groups; an aryloxy group (an aryloxy group having from 6 to 39 carbon atoms, e.g., phenoxy, p-methoxyphenoxy, m-octyloxyphenoxy, o-chlorophenoxy, 2,4-di-t-octylphenoxy); an alkoxycarbonyl group (an alkoxycarbonyl group having from 2 to 39 carbon atoms, e.g., methoxycarbonyl, ethoxycarbonyl, n-butoxycarbonyl, isopropoxycarbonyl, t-butoxycarbonyl, n-octyloxycarbonyl, n-dodocyloxycarbonyl, pentadecyloxycarbonyl, stearyloxycarbonyl, oleyloxycarbonyl, docosyloxycarbonyl), in addition to the above, alkoxycarbonyl groups derived from higher alcohols such as Fine Oxocol 140, 1600, 1800, 180, 180N, 2000 and 2600 (trade names, produced by Nissan Chemical Industries, Ltd.) can also be included in specific examples of alkoxycarbonyl groups; an aryloxycarbonyl group (an aryloxycarbonyl group having from 6 to 39 carbon atoms, e.g., phenoxycarbonyl, p-ethoxyphenoxycarbonyl, m-dodecyloxyphenoxycarbonyl o-chlorophenoxycarbonyl, 2,4-di-t-octylphenoxycarbonyl); a carbamoyl group (a carbamoyl group having from 3 to 39 carbon atoms, e.g., dimethylcarbamoyl, diethylcarbamoyl, dioctylcarbamoyl, distearylcarbamoyl, dioleylcarbamoyl, bis(2-ethylhexyl)carbamoyl, stearyloxypropylcarbamoyl); and xe2x80x94NR5R6 (xe2x80x94NR5R6 having from 1 to 39 carbon atoms, e.g., octylamino, dioctylamino, stearylamino, distearylamino, oleylamino, dioleylamino, methylamino, anilino).
When R2 represents a substituted alkyl group, the sum total of the carbon atom number is preferably from 14 to 35, more preferably from 18 to 30.
When R2 represents an alkyl group, an unsubstituted straight chain alkyl group having from 18 to 30 carbon atoms is most preferred.
When R2 represents an alkenyl group, the sum total of the carbon atom number is preferably from 18 to 34. A specific example of the unsubstituted alkenyl group includes the following structure: 
Further, specific examples of substituted alkenyl groups include the following structures: 
When R2 represents an aryl group, the sum total of the carbon atom number is from 14 to 40, preferably from 18 to 35.
When R2 represents an aryl group, a substituted aryl group is preferred to an unsubstituted aryl group. Examples of substituents of the aryl group include a carboxyl group, a sulfo group, an aryl group, a cyano group, a nitro group, an arylcarbonyl group, an alkylcarbonyl group, a carbamoyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, an acylamino group, an aryloxycarbonylamino group, an alkoxycarbonylamino group, an arylsulfonylamino group, an alkylsulfonylamino group, an aminocarbonylamino group, a sulfamoylamino group, xe2x80x94NR5R6 (R5 and R6, which may be the same or different, each independently represents an alkyl group, an aryl group or a hydrogen atom), an alkoxyl group, an aryloxy group, a heterocyclic oxy group, an alkylthio group, an arylthio group, a heterocyclic thio group, an alkylsulfonyl group, an arylsulfonyl group, a phosphoryl group, a halogen atom, a hydroxyl group, an acyloxy group, an alkenyl group, an alkyl group and a heterocyclic group.
Of these, an arylcarbonyl group, an alkyl group, an alkylcarbonyl group, a carbamoyl group, an acylamino group, an arylsulfonylamino group, an alkylsulfonylamino group and an alkoxyl group are preferred.
Specific examples thereof include an arylcarbonyl group (an arylcarbonyl group having from 7 to 34 carbon atoms, e.g., benzoyl, p-toluyl, m-chlorobenzoyl, o-methoxybenzoyl, p-octyloxybenzoyl, m-stearoylaminobenzoyl), an alkylcarbonyl group (an alkylcarbonyl group having from 2 to 34 carbon atoms, e.g., acetyl, n-propionyl, pivaloyl, n-octylcarbonyl, n-stearoyl, n-lauroyl, 2-methoxyoctylcarbonyl), a carbamoyl group (a carbamoyl group having from 1 to 34 carbon atoms, e.g., methylcarbamoyl, dimethylcarbamoyl, isobutylcarbamoyl, cyclohexylcarbamoyl, n-octylcarbamoyl, di-n-octylcarbamoyl, oleylcarbamoyl, dimyristylcarbamoyl, N-methyl-N-phenylcarbonyl), an acylamino group (an acylamino group having from 2 to 34 carbon atoms, e.g., acetylamino, pivaloylamino, propionylamino, stearoylamino, lauroylamino, benzoylamino, p-stearyloxybenzoylamino), an arylsulfonylamino group (an arylsulfonylamino group having from 6 to 34 carbon atoms, e.g., benzenesulfonylamino, toluenesulfonylamino, p-bromobenzenesulfonylamino), an alkylsulfonylamino group (an alkylsulfonylamino group having from 1 to 34 carbon atoms, e.g., methanesulfonylamino, ethanesulfonylamino, n-butanesulfonylamino, n-octanesulfonylamino), an alkyl group (an alkyl group having from 1 to 18 carbon atoms, e.g., methyl, ethyl, t-butyl, t-octyl), and an alkoxyl group (an alkoxyl group having from 1 to 34 carbon atoms, e.g., methoxy, ethoxy, isopropoxy, octyloxy, stearyloxy), in addition to the above, alkoxyl groups derived from higher alcohols such as Fine Oxocol 140, 1600, 1800, 180, 180N, 2000 and 2600 (trade names, produced by Nissan Chemical Industries, Ltd.) can also be included in specific examples of alkoxyl groups.
When R2 represents an alkoxyl group, the sum total of the carbon atom number is from 14 to 40, more preferably from 18 to 35. The alkoxyl group may further be substituted, and those described as substituents which may be substituted when R represents an alkyl group or an aryl group can be cited as substituents of the alkoxyl group.
Examples of alkoxyl groups include stearyloxy, myristyloxy, eicosyloxy and the structural formula shown below: 
When R2 represents xe2x80x94NR3R4 (R3 and R4 each independently represents an alkyl group having from 1 to 40 carbon atoms, a hydrogen atom, or an aryl group), the xe2x80x94NR3R4 group has the sum total of from 14 to 40 carbon atoms, more preferably from 18 to 35. Specific examples of xe2x80x94NR3R4 include distearylamino, dimyristylamino, dioctylamino, di(2-ethylhexyl)amino, stearylamino, lauryloxypropylamino, and anilino.
When R2 represents a bicycloalkenyl group or a bicycloalkyl group, the sum total of the carbon atom number is from 14 to 40, preferably from 18 to 35. The bicycloalkenyl group or bicycloalkyl group preferably has [2,2,1] or [2,2,2]-bicyclo structure. Specific examples thereof include the following: 
When R2 represents a cycloalkenyl group or a cycloalkyl group, the sum total of the carbon atom number is from 14 to 40, preferably from 18 to 35. Specific examples of cycloalkenyl groups include 2-octyloxy-4-cyclopenten-1-yl and 4-stearyloxycarbonyl-2-cyclohexen-1-yl, and specific examples of cycloalkyl groups include 2-undecyloxycyclopentyl and 4-octyloxycarbonylcyclohexyl.
When R2 represents a heterocyclic group, the sum total of the carbon atom number is from 14 to 40, preferably from 18 to 35. Specific examples of heterocyclic groups include the following: 
Of the above-described substituents, R2 preferably represents a substituted or unsubstituted alkyl group having the sum total of from 14 to 40 carbon atoms, more preferably a substituted or unsubstituted alkyl group having the sum total of from 18 to 35 carbon atoms.
The compound represented by formula (I) preferably has the structure in which R2 represents a substituted or unsubstituted alkyl group having the sum total of from 14 to 40 carbon atoms, R1 represents an unsubstituted alkylene group having from 1 to 3 carbon atoms, and X is represented by formula (V).
Above all, the structure in which R2 represents a substituted or unsubstituted alkyl group having the sum total of from 18 to 40 carbon atoms, R1 represents a methylene group, and X represents xe2x80x94COxe2x80x94OH is most preferred.
Specific examples of the compounds for use in the present invention are shown below, but the present invention is not limited thereto.
General synthesis methods of the compounds of the present invention are shown below.
The compound of the present invention can be obtained by condensing the corresponding carboxylic acid chloride and a hydroxylamine. When the corresponding carboxylic acid is easily available, carboxylic acid chloride can easily be obtained by treating the carboxylic acid with thionyl chloride or oxalyl chloride. When the corresponding carboxylic acid is a complicated carboxylic acid, carboxylic acid chloride can be obtained by synthesizing the carboxylic acid according to a suitable synthesis method and treating the carboxylic acid with thionyl chloride or oxalyl chloride. Carboxylic acids can be synthesized according to the following synthesis methods. 
When X is represented by formula (III) or (IV), there is a case where the synthesis yield of acid chloride according to the above reaction scheme is low. In such a case, it is preferred to protect X with a protective group temporarily and release the protective group after the reaction of acid chloride and hydroxylamine.